Conversion of hydrocarbonaceous material into synthesis gas



June 11,1957 JACOL'VEV ETAL 'Re. 24,328

CONVERSION 0F HYDROCARONACEOUS MATERIAL I'NTo SYNTHESIS GAS OriginalFiled MarchZ?. 1948 frozen/:Ys

United States Patent O CONVERSION OF HYDROCARBONACEOUSy MATERIAL INTOSYNTHESIS GASl Leon Jacolev, Montclair, N. I., and Leon P. Gaucher,Beacon, N. Y., assignors to The Texas Company, New York, N. Y., acorporation of Delaware Original No. 2,606,326, dated August 12, 1952,Serial No. 17,518, March Z7, 1948. Application for reissue August 16,1956, Serial No. 604,580

4 Claims. (Cl. IS-196) Matter enclosed in heavy brackets [j appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

The present invention relates to the production of synthesis gascontaining hydrogen and carbon monoxide in relative proportions suitablefor the catalytic synthesis of hydrocarbons and the like, and is moreparticularly concerned with the conversion of hydrocarbonaceousmaterials into maximum yields of synthesis gas containing a desirablyhigh porportion of hydrogen to carbon monoxide.

In accordance with the invention, a substantially mproved yield of highpurity synthesis gas is realized on the basis of minimum fuel andmolecular oxygen requirements by subjecting a hydrocarbon to partialcombustion with molecular oxygen and thereafter utilizing the sensibleheat of the combustion products to support the endothermic catalyticreaction of additional hydrocarbon with water vapor and thus supplementthe overall product, particularly in respect to the hydrogen contentthereof.

More specifically, a hydrocarbon such as methane is subjected to partialcombustion with a proper proportion of molecular oxygen, advantageouslya pure or enriched stream containing 50 to 100 percent, and preferablymore than 90 percent, of molecular oxygen at an elevated temperature atwhich maximum practical yields of hydrogen and carbon monoxide result.

The temperature of the combustion zone is maintained at as high a levelas possible, for example, above about 2000 F., and preferably above 2300to 2400 F., e. g., 2900 to 3000 F. where feasible. In general, highertemperature of reaction means greater yield of hydrogen and carbonmonoxide.

The sensible heat of the hot eiuent products of reaction is thereafterindirectly transferred to support the endothermic reaction of additionalhydrocarbon with water vapor in the presence of a catalyst. Thetemperature of the endothermic reaction zone is in the range at whichthe hydrocarbon-steam reaction, by virtue of the catalyst, progresseselectively to produce high yields of additional hydrogen and carbonmonoxide having a relatively high molar ratio of hydrogen to carbonmonoxide, which range, however, is suihciently below the temperature ofhot gases from the combustion zone to permit ecient heat transfer.

Advantageously, the transfer of heat energy from the hot effluent gasesof the combustion zone is elected as rapidly as possible, preferably ata rate akin to quenching, so that the equilibrium relationship of thehot effluent gaseous stream is not materially altered. To this end, itis advantageous to conduct the heat transfer through the medium of adense fluid phase mass of preferably inert, solid particle material inindirect heat exchange relationship with the catalyst containing zone,herein known as the hydrocarbon-steam, or methane-steam reforming zone.Thus, the high temperature synthesis gas from Re. 24,328 Reissued June11, 1957 the partial combustion of the hydrocarbon with molecular oxygenmay be continuously conducted upwardly into a substantial mass of thesolid inert material in dense fluid phase at a rate sufficient tomaintain particle tluidization, simultaneously experiencing a sharptemperature drop'to the lower temperature at which the solid iscontinuously maintained by regulated heat transfer to the methane; steamreforming zone;

In this way, the high temperature gas stream is rapidly cooled withoutmaterial loss of desired constituents and sutiicient heat energy is madeavailable by Virtue of sucli cooling to effect the catalytic endothermicreforming of substantial additional quantities of methane without theexpenditure of additional fuel or molecular oxygen. So also as abovestated, the overall proportion of the hydrogen produced issimultaneously increased.

The invention is accordingly of particular advantage in effectingmaximum conversion of hydrocarbons into high purity synthesis gas with aminimum consumption of pure molecular oxygen and of extraneous fuel. Itis also of particular advantage in elfecting an appreciable increase inH2:CO ratio without the expenditure of additional thermal energy. Thisfollows from the discovery that the exothermic partial combustion stepand the endothermic methane-steam reforming step operate separately togive highest overall yields of hydrogen and carbon monoxide. Where theproducts of partial combustion dilute the reactants of the methane-steamreforming step yields are materially impaired.

For example, the partial combustion of a hydrocarbon under conditions ofgood yeld results in-a product having a substantially lower proportionof hydrogen than would be indicated by the stoichiometric relationshipsinvolved; thus, the partial combustion of methane with pure oxygen undermore or less ideal commercial conditions of operation only results in aproduct having a molar ratio of hydrogen to carbon monoxide in theneighborhood of 1.85 l. Obviously, since the products formed bycatalytic conversion of synthesis gas into liquid hydrocarbons usuallyhave a collectively higher H2:CO ratio, such a feed is not conducive ofmaximum theoretical yields. Moreover, a relatively higher proportion ofhydrogen is usually advantageous in effecting the catalytic conversionof the reactants to hydrocarbons in the synthesis zone.

Moreover, with hydrocarbon starting materials other than methane, thediscrepancy is more pronounced since higher hydrocarbons contain a lowerrelative proportion of hydrogen than methane and yield synthesis gas ofcorrespondingly reduced hydrogen to carbon monoxide ratio.

It has been proposed to alleviate this condition by converting a portionof the product carbon monoxide into hydrogen by means of the water-gasshift reaction, by adding steam to the zone of partial combustion, or bysubjecting the product, together with additional hydrocarbon and steam,to catalytic reforming. These proposals are unsatisfactory, however, inthat they result in a varying though usually quite substantial loss ofyield. Thus, for example, the addition of endothermically reacting watervapor to the zone of partial combustion inherently results in a loweredreaction temperature and accordingly a less favorable reactionequilibrium. These results appear to adversely affect product yield.Subsequent catalytic processing in the presence of added steam has asimilar effect. Separate water-gas shifting obviously consumes desiredcarbon monoxide and involves processing losses.

lt has been discovered that, in accordance with the present invention,these defects are substantially overice come and a novel and surprisingincrease in the yield of desired product is realized through theexpenditure of a portion of thevwaste heat in the hot eflluent gasesfrom the combustion zone.

Partial combustion of methane may be elfected at the desired hightemperatures mentioned above in the presence preferably of relativelypure oxygen such that the proportion of oxygen is in the range up toabout 20 'percent excess over the stoichiometric quantity indicated forconversion of the hydrocarbon to hydrogen and carbon monoxide, that is,in the range of about 1.0 to about 1.3 atoms of oxygen per atom ofcarbon.

While the partial combustion may Vary widely, the invention particularlycontemplates effecting the reaction at., or preferably above,atmospheric pressure under the conditions described in detail in theeopending application 717,267, led December 19, 1946, now abandoned, towhich reference is hereby made for details. More specifically, thereaction zone is preferably free from internal packing or catalyst, andhas an internal length-to-radius ratio within the range of about0.67:l-lO:1, preferably about 1:1-4zl. As a result of this feature, thereactants tend to reach an equilibrium condition corresponding tomaximum yield, with due regard to prevention of carbon formation and thelike.

The hot products of reaction ow from the zone of partial combustiondirectly into a dense lluid phase of inert solid particles at a lowertemperature in the range of from about 1200 to 2000 F., but preferablyabout 1500 to 1800 F., transferring heat indirectly to the endothermicmethane-steam reforming step.

In order to explain the invention in greater detail reference is had tothe accompanying drawing, representing more or less diagrammatically twospecic embodiments thereof.

In Fig. l, an incoming stream of a hydrocarbon gas, such as methane, isintroduced through line 10, the major portion of this stream passing viapipe 28 to burner nozzle 11. A stream of oxygen of greater than 95percent purity is supplied through pipe 12 to an internal passage of theburner 11. The two streams of gas emerge from respective concentricorifices of the mixing nozzle 11 into the interior 13 ofa combustionchamber 14, in the relative proportion for partial combustion describedabove. Preferably, the reactant streams in pipes 10 and 12 are preheatedto as high a temperature as is feasible, for example, 800-l000 F. orabove so that the resulting temperature of the combustion zone 13 iscontinuously maintained at a high level, for example, 2300-2400 F.Preheating may be effected by the waste heat in the nal product gas, orby any other convenient means.

The euent synthesis gas comprising hydrogen and Ycarbon monoxide in themolar ratio of about 1.85 to 1, at the elevated temperature of the zoneof partial combustion, passes through a short conduit 16 into theconical bottom 18 of an exchanger 19, provided with a preferably denseuid phase of suitable, inert, powdered solid material 20. The powder ofthe fluid phase may comprise sand, clay, silica, carborundum or anyrelatively inert solid, preferably in the particle size range of lfromabout l mesh down to 400 mesh and finer. Advantageously, the uid phasecondition is maintained by the upow of reactants. The product gasemerges from the upper pseudo-liquid level 22 of the fluid phase andpasses through a filter 23 and outlet pipe Z4 to a cooling exchanger 26.

Meanwhile ,a minor stream of methane is withdrawn from pipe into branchpipe 29 where it is admixed with at least an equal molecular proportionof high temperature steam from pipe 30. The mixture passes by way of aheader 32 through a plurality of pipes 33 packed with methane-steamreforming catalyst, and disposed in heat exchange relationship with thehot fluid phase of inert solid within the exchanger 18. Morespecifically, the pipes 33 continually absorb thermal energy from thedense uid phase at a rate sucient to thermally support the reformationof methane and steam into additional synthesis gas, approximately inaccordance with the reaction:

The converted or reformed products are received by the outlet header 35and pass by way of pipe 36 through a cooling exchanger or condenser 37into a separator 38, from which any contained moisture is removed as at39. The dry product separated at 38 passes overhead at 42 and admixeswith the cooled gases from the exchanger 26, injected by way of pipe 43.

In the embodiment of Fig. 2, the reforming catalyst is likewisemaintained in a dense fluid phase in order to facilitate heat transferand maintain temperature uniformity therein. To this end, thehydrocarbon-steam reforming zone comprises a series of vertical tubes 50distributed more or less uniformly through the fluid phase of inertsolid 20, and containing the reforming catalyst in solid particle form.Each of the tubes 50 has a preferably conical lower extremity 52 to theapex of which inlet pipes S3 connect. As indicated, the inlet pipes 53join with suitable bustle tubes or headers 54 which receive thereforming feed through pipe 29 as above.

The reaction products from the reformer tubes 50 are received in asuitable streamlined header S5 and discharged through a pipe 36.

The outlet pipe 24 of the exchanger is provided with a cyclone separator57 in lieu of filter 23 for removing any possibly entrained solidparticles, which are discharged as at 5S. Otherwise, the embodimentdescribed in Fig. 2 follows the construction previously disclosed.

In operation it will be appreciated, from the above, that the thermalrequirements of the endothermic methane-steam reforming operationcarried out within the catalyst tubes 33 or 50 determine the temperatureof the uid phase 20. In turn, the thermal requirements of reforming maybe controlled by adjusting the rate of feed of the reactants, namely,hydrocarbon gas and steam supplied thereto. This is balanced with thesensible heat available in the hot gaseous stream supplied through pipe16 so that the reforming zone operates continually at a reformingtemperature of from 1500 to 2000 F., for example.

It has been found that in the case of methane, an additional quantity offrom l0 to 20 percent and frequently up to 30 percent can be thusreformed by the thermal energy available in the hot combustion gases.

For example, operating as above, the generator gases at a temperature ofabout 2400 F., meeting the dense uid phase in the exchanger 18, coolrapidly to a temperature just above 1600 F. uniformly prevailing in thefluid phase. This, in turn, holds the temperature within tubes 33 atabout 1600 F. The stream of reactants passing through the reformingtubes 33 comprises methane, equal in quantity to about 20 percent ofthat being supplied to the combustion zone, in admixture with a molarquantity of steam equal to about twice that of the methane. Preferably,the mixture is preheated to, for example, about 1000* F. Under theseconditions, the process proceeds to operate continuously, as indicated,with the products of catalytic reforming comprising a synthesis gas of ahigh hydrogen to carbon monoxide ratio supplementing the yield ofproduct from the combustion zone.

For example, the following table compares results using natural gascomprising mainly methane with minor quantities of higher hydrocarbongases, corresponding overall to the empirical formula C1u42 Heuss:

6 From the foregoing, it is apparent that the present invcntion permitsthe production of synthesis gas more ideally suited to the directcatalytic production of hydrocarbons, not merely without loss of yield,but actually Feed to Zone of Partial Partial Combustion Zone Feed toMeth- Combustion: Mols Product: Mols ane-Steam Re- Final Mixed Product:Mols Total Feed: Mols Run forme-r: Mols Nat. Pure Steam H; O0 Ha/OOH1+CO Nat. Steam H2 CO Hz/OO Hr-I-CO Nat. Pure Steam Gas Oz Gas Gas Oi A100. 61. 9 None 187. 101. 1. 85 288. Y 20. l2 40. 24 239. 9 113. 8 2. l353. 7 120. 12 61. 9 40. 24 B 120. 12 74. 35 d0. 224. 6 121. 35 1. 85345. 95 224. 6 121. 35 1. 85 345. 95 120.12 74. 35 C 100. 61. 9 d0 187.101. 1. 85 288. 20. l2 40. 24 221. 8 101. 67 2. 1 323. 51 120. 12 61. 940. 24

In each of the cases covered, all reactants are preheated toapproximately 1000 F. and the reactions carried out under a pressure of250 p. s. i. g. The reforming catalysts comprises nickel oxide togetherwith aluminum silicate.

In run A, the initial feed of natural gas and oxygen in suitableproportions for high yield of synthesis gas is reacted in a zone ofpartial combustion, yielding a product gas at about 2400 F. containing(basis 100 mols natural gas fed), 288 mols of hydrogen and carbonmonoxide in the molar ratio of 1.85 to l; thereafter, approximately 20mol percent additional natural gas is reacted with steam at atemperature of 1600 F., continuously maintained by heat tnansfer fromthe hot products of the combustion zone, to give a total yield of 353.7mols in the molar ratio of 2.1 to 1.

Run B compares the results of burning the same total quantity of naturalgas with the same relative proportion of oxygen but without reforming.It is of striking significance, that, in spite of the increasedconsumption of oxygen, the overall yield of hydrogen and carbon monoxideis substantially less than in run A, and the hydrogen to carbon monoxideratio of the product is only 1.85 to 1. Combustion temperature is thesame as in the previous run.

Run C compares an operation where the partial combustion zone -isoperated identically as in Run A, the hot eiuent gases being thereafteradmixed with natural gas and steam, equivalent to that reformed in runA, and the mixture pased in Contact with a methane-steam reformingcatalyst. The results particularly emphasize the substantial loss ofyield of total hydrogen and carbon monoxide encountered in compensatingfor the increased hydrogen to carbon monoxide ratio resulting from this:method. The reduced yield is believed particularly striking in view ofthe fact that reforming temperature in this run, due to inherentlydecreased conversion, rises to the more favorable level of about 1770 F.

In accordance with an additional example wherein. quantities of totalfeed materials identical with those employed in runs A and C areintroduced simultaneously into the zone of partial combustion, theresults are substantially identical with those indicated for run C.. Inthis case, reactant preheat is identical with the preheat conditionsobserved in the other runs, and reaction is carried out under a pressureof 250 p. s. i. g.

It is significant to note that in the final example asI well as in runC, the loss of desired product yield is. accompanied by a substantialappearance of methane inthe final product amounting to more than 12 molson the: foregoing basis of 100 mols of natural gas supplied to the zoneof partial combustion. This constitutes ap proximately three percent onthe basis of the total yield of hydrogen and carbon monoxide, ascontrasted with only slightly greater than one percent of methane on thesame basis in the product of run A. It follows` therefore that, inaddition to the improved yields shown above, the present inventionmaterially overcomes contamination of the product by unreactedhydrocarbon.

with a surprising increase in overall yield. This effect is achievedwithout increase in the pure oxygen requirement. Moreover, both theendothermic and exothermic 0 reactions proceed continuously Without thenecessity for supplying external heat energy to the reaction zones. Inparticular, the process eliminates the necessity for combustion ofadditional fuel to furnish the thermal requirements of the catalyticendothermic reforming step. p

While the invention has been described above with particular referenceto methane and similar hydrocarbons, it is applicable in its broadestaspect to the treatment of hydrocarbonaceous feed materials in general.Advantageously, normally liquid hydrocarbons are vaporized by preheatingbefore introduction into the reaction zones. In its broadest aspect, theinvention contemplates the use of solid carbonaceous fuels, preferably,however, in a powdered or disintegrated form.

As intimated above, the invention is particularly advantageous in theconversion of hydrocarbons having a lower atomic H/C ratio than methane,as for example, ethane, propane, butane and the like. This followsbecause the proportion of hydrogen in the synthesis gas producedtherefrom tends to be correspondingly reduced.

The invention also contemplates particularly the conversionof liquidhydrocarbons wherein the atomic H/C ratio is usually not substantiallygreater than 2:1. In spite of the fact that the resulting synthesis gasmay require additional fortification with hydrogen, nevertheless theimprovement achieved by the present invention may frequently be adequatein itself, and in any event, obviously contributes to economicaloperation.

In this connection, it is moreover perti-nent to point yout that in thecase of the higher hydrocarbons, particularly liquid fuel oils and evenmaterials of a character such as tar and coke, the exothermic heatenergy made available in the zone of par-tial combustion issubstantially greater than that resulting from the partial combustion ofmethane and thus permits a materially increased amount of reforming inthe hydrocarbon-steam reforming zone.

So also, the increasing heat liberation in the case of higherhydrocarbons, usually makes it advisable as Well as necessary to includea limited addition of steam `or carbon dioxide in the feed to thecombustion zone to prevent excessive temperature rise. The amount soadded should be suicient to hold the temperature at a .level compatiblewith the structural limitations met with in practical operations, butnot sufficient to lower the temperature below the optimum rangediscussed above. It may be substantial in the case of heavy oils andcoals in spite of the fact that it cannot usually be tolerated, to anyappreciable extent, in the case of light hydrocarbon gases due toexcessive reduction of op erating temperature.

Obviously, from the foregoing, the process of this invention results inmaximizing eiciency in respect to pure oxygen consumption andcompensates in part for the relatively low hydrogen content of thehigher hydrocarbonaceous starting materials. l

The term molecular oxygen as employed herein refers to free oxygen ascontrasted with combined oxygen, of water vapor or such as frequentlyoccurs in coals or other hydrocarbonaceous materials.

As indicated above, no invention, per se, is involved in the methanereforming catalyst, which may include any conventional catalysteffective for promoting the reforming of hydrocarbon by steam. Suchcatalysts conventionally consist of metal oxides, such as nickel orcobalt oxides, frequently in admixture with thoria or other oxides ofthe rare earths. Particularly effective catalysts for this purpose arethe iron and nickel oxides, together with compounds of aluminum oxideand silica or boron and phosphorus, for example, aluminum silicate,bauxite, kaolin and the like. Nickel or cobalt oxide, promoted byalumina and supported by unglazed porcelain, is another example.

While mention has been made of the advantage of effecting heat transferthrough the medium of a mass of inert solid particles maintained indense fluid phase,

the invention in its broadest aspect is not so limited, but

contemplates transfer of sensible heat from the combustion gases tothe-hydrocarbon-steam reforming zone by any suitable effective indirectheat transfer instrumentality.

Obviously, many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

What we claim is:

l. The method of converting carbonaceous material containing hydrogeninto high yields of synthetic gas containing a mixture of hydrogen andcarbon monoxide of relatively high hydrogen content, which comprisesreacting said carbonaceous material in a partial combustion zonemaintained above about 2000 F., with substantially pure oxygen in aproportion effective to result in a gaseous product composed essentiallyof H2 and CO, injecting the hot elluent product gas into a dense fluidphase of solid particle marterial continuously maintained at asubstantially lower temperature, thereby effecting continual quenchingof the hot, effluent product gas and containually maintaining the saiddense uid phase of solid particle material at said substantially lowertemperature by transferring thermal energy therefrom into a reformingzone disposed in heat transfer relationship therewith, passing a mixedstream of hydrocarbon and steam upwardly through said reforming zone,maintaining within said reforming zone a dense duid phase of particulatesolid reforming catalyst active at the temperature prevailing therein toconvert said mixed stream of hydrocarbon and steam into H2 and CO, andintroducing said mixed stream of hydrocarbon and steam into thereforming zone 4at a rate sufficient to support said reforming catalystin dense uid phase condition as aforesaid, and to regulate theendothermic reaction of said hydrocarbon and steam in said reformingzone such that said uid phaseof solid particle material is maintainedthereby at said lower temperature.

2. The method of converting a gaseous hydrocarbon into hydrogen andcarbon monoxide which comprises oxidizing a stream of said hydrocarbonin a zone of partial combustion at a temperature in excess of about 2000F. in the presence of molecular oxygen in a proportion effective toyield approximately maximum quantitles of hydrogen and carbon monoxide,injecting [rapidly cooling the] hot efiluent gaseous products of thezone of partial combustion into a dense fluid phase of solid particlematerial disposed [by passing said products] in [indirect] heat exchangerelationship with an endothermic reaction zone containing a catalysteiective to convert mixture of hydrocarbon and steam directly intohydrogen and carbon monoxide at an elevated operating temperaturesubstantially below the temperature of the hot eiuent products of thezone of partial combustion, continuously feeding a stream of hydrocarbonand steam into contact with said catalyst at a rate such that saidendothermic reaction zone is maintained continuously at said operatingtemperature, continuously withdrawing products of reaction from contactwith said catalyst after substantial conversion has occurred, andadrnixing the product gas from the endothermic reaction zone with thecooled product gas from the partial combustion zone.

l[3. The method according to claim 2 wherein the operating temperaturemaintained in the endothermic zone by indirect heat exchange with thehot efuent products of partial combustion is within the range above l500R] [4. The method according to claimk 2 wherein rapid cooling of the hoteffluent from the zone of partial cornbustion in indirect heat exchangewith the endothermic reaction zone is effected by injecting said hoteffluent into a `dense fluid phase of solid particle material disposedin heat exchange relation with the said endothermic zone] [5, The methodof converting a gaseous hydrocarbon into hydrogen and carbon monoxidewhich comprises oxidizing a stream of said hydrocarbon in a zone ofpartial combustion at a temperature in excess of about 2000 F. in thepresence of molecular oxygen in a proportion effective to yieldapproximately maximum quantities of hydrogen and carbon monoxide,rapidly cooling the hot eluent gaseous products of the zoneof partialcombustion by passing said products in indirect heat exchange with anendothermic reaction zone containing a catalyst effective to convertmixtures of hydrocarbon and steam directly into hydrogen and carbonmonoxide at an elevated operating temperature substantially below thetemperature of the hot efuent products of the zone of partialcombustion, continuously feeding a stream of hydrocarbon and steam intocontact with said catalyst at a rate such that said endothermic reactionzone is maintained continuously at said operating temperature, andcontinuously withdrawing products of reaction from contact with saidcatalyst after substantial conversion has occurred] 6. The method ofconverting a gaseous hydrocarbon into hydrogen and carbon monoxide whichcomprises splitting said gaseous hydrocarbon feed into two streams,

`oxidizing one of said streams of hydrocarbon in a zone of partialcombustion at u temperature in excess of about 2000* F. in the presenceof molecular oxygen in a proportion eective to yield approximatelymaximum quantites of hydrogen and carbon monoxide, rapidly cooling thehot eluent gaseous products of the zone of partial combustion by passingsaid products in indirect heat exchange with an endothermic reactionzone containing a catalyst eective to convert mixtures of hydrocarbonand steam directly into hydrogen and carbon monoxide at an elevatedoperating temperature substantially below the temperature of the hoteluent products of the zone of partial combustion, continuously feedingthe other of said streams of hydrocarbon in admixture with steam intoContact with said catalyst at a rute such that said endothermic reactionzone is maintained continuously at said operating temperature, andcontinuously withdraw- (References on following page) References Citedin the fle of this patent or the original patent UNITED STATES PATENTSRussell et al. Mar. 20, 1934 5 Wietzel et a1 May 8, 1934 Beekley Aug.18, 1936 Murphree et a1 Aug. 19, 1947 10 Rees et al Nov. 1, 1949 PeeryJan. 3, 1950 Mader Dec. 25, 1951 Alexander et al Nov. 18, 1952 OTHERREFERENCES Taylor: Industrial Hydrogen, page 150.

